HP J2415A Installation And Reference Manual page 76

Hub Reference
The Uplink port is a special promiscuous LAN port. As a promiscuous port,
it sends and receives all packets to and from the upper-level hub. It is a
special port because it can transmit multiple packets to the upper-level hub
(for example, to accommodate the multiple end nodes that may be
connected to the lower-level hub).
N o t e
The Uplink port can only be used to connect to an upper-level hub or switch
and requires an unbundled LAN cable. The use of the Uplink port to connect
to an end node or similar device is not supported.
Optional Downlink Port (12B) This port can be used to create a
fiber-optic backbone to another Hub-14 by installing fiber-optic transceivers
into both hubs. If you do not want to use redundant uplinks and would
rather use the modular port as a flexible media downlink port, you can
connect a cable to the port labeled "Uplink B or 12B". Before or after you
connect the cable to this port, use HP Stack Manager or HP Interconnect
Manager to specify that this port is to be used as a downlink port rather than
an uplink connection (default).
Cable Management Bar
A cable management bar helps you manage the routing of your cables. For
more information, refer to chapter 1, "Installing the HP AdvanceStack Hub".
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